1. Field of the Invention
This invention relates to a resin composition and a resin-molded type semiconductor device wherein a semiconductor chip is sealed with the resin composition being cured.
2. Description of the Related Art
With the current trend to achieve an increased integration of a semiconductor element, the miniaturization of various function units of the element and the enlargement of the element per se are now progressing. For the purpose of sealing such semiconductor chip with a resin composition, an epoxy resin composition comprising a thermosetting epoxy resin as a main component and a phenol resin as a curing agent has been extensively employed.
For example, a gate array of so-called ASIC (Application Specific IC) or a surface mount type package represented by a standard cell type LSI has been produced by making use as a sealing resin of an epoxy resin. In the process of mounting these semiconductor devices on a substrate, a thermal treatment such as a vapor phase reflow, an infra-red ray reflow and a solder dipping is performed. In this thermal treatment, the package is exposed to a high temperature in the order of 215 to 260.degree. C., so that a trace of water which has been penetrated into the package is suddenly vaporized, thus often giving rise to the generation of a crack in the sealing resin.
When the crack is extended to the external surface of the sealing resin, the moisture resistance reliability of resin-molded type semiconductor device will be damaged raising a serious problem. Moreover, when a crack is generated in the sealing resin, the resin will be caused to swell resulting in the deformation of the package, thus possibly making it difficult to mount the package on a substrate.
Furthermore, when such a defective package is mounted on a substrate, various problems including a cracking may be brought about even in the interior of the semiconductor chip sealed with a resin. For example, PSG (phosphosilicate glass) or SiN (silicon nitride) which is used as a passivation film for a metallic interconnecting wiring layer formed of aluminum for example may be cracked, or the breakage of a gold bonding wire may be caused.
To solve these problems, there have been various demands as described below in the manufacture of a resin molded package in particular of large size, these demands being mainly related to the sealing resin.
(1) The stress to be laid upon inner devices by the sealing resin should be minimized, and the adhesion between the sealing resin and a lead frame or a film such as PSG film, SiN film or polyimide film formed on a semiconductor chip should be improved.
(2) The sealing resin should be excellent in heat resistance, i.e., sufficiently high in high-temperature strength or in high-temperature strength under moisture absorption so as to withstand the mounting temperature of the package. At the same time, the hygroscopicity of the sealing resin should be as low as possible.
In view of these demands, there has been studied to use, as a main component of a sealing resin composition for a semiconductor chip, a heat-resistive thermoplastic resin of so-called engineering plastic such as PPS (polyphenyl sulfide) resin, PPE (polyphenylene ether) or liquid crystal polymer. However, it is required to heat them at a relatively high temperature in the range of 200 to 300.degree. C. in order to melt-molding these resins. Moreover, there is a problem that the melt viscosity of these resins is higher than that of epoxy resin. Since these resins are accompanied with these problems, the molding of them is very difficult as compared with the conventional sealing resin composition containing epoxy resin.
The conventional sealing resin composition for a semiconductor chip generally contains about 50 to 85 parts by weight of an inorganic filler in order to lower the thermal expansion coefficient of the sealing resin composition and at the same time to improve the thermal shock resistance of the sealing resin composition. However, if the thermal shock resistance of the aforementioned heat resistance thermoplastic resin is to be improved by the addition in the equal volume of inorganic filler, the melt viscosity of the sealing resin would be further increased thus deteriorating the flowability of the sealing resin, thus inviting the drifting of bonding wire or the dislocation of the bed. On the other hand, if a resin of lower molecular weight is employed, the melt viscosity of the sealing resin may be lowered thereby improving the moldability of the sealing resin, but the strength and heat resistance of the sealing resin would be deteriorated.